JP6953862B2 - Fuel injection control device - Google Patents

Description

The present invention relates to a fuel injection control device for an internal combustion engine.

As a fuel injection valve that injects and supplies fuel to each cylinder of an internal combustion engine mounted on a vehicle or the like, for example, an electromagnetic solenoid type that operates by electric power supplied from an in-vehicle battery is known. In this type of fuel injection valve, the fuel injection control device controls the energization timing and energization time of the coil built in the fuel injection valve body to drive the valve body (needle) in the valve opening direction. It controls the fuel injection timing and fuel injection amount.

In recent years, in order to optimize the fuel injection amount and the like, consideration has been given to variations in fuel injection valves and temperature changes. Specifically, the fuel injection control device takes measures such as feedback-controlling the drive current in the fuel injection valve to obtain a constant fuel injection amount (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-163549

However, due to differences in the circuit elements that make up the current detection circuit that detects the current value of the drive current (for example, the difference in shunt resistance), there is an error between the detected current value of the drive current and the actual current value of the drive current. May occur. In this case, there is a problem that the control cannot be performed correctly.

The present invention has been made in view of the above problems, and a main object thereof is to provide a fuel injection control device for appropriately correcting a detection error of a current value.

The fuel injection control device for solving the above problems includes a coil that is energized based on a voltage applied from the power supply unit, a fuel injection valve having a valve body that opens and closes according to the energization of the coil, and a voltage applied from the power supply unit. It is applied to a fuel injection system including a current detection unit that detects a current value when the above is performed. This fuel injection control device determines the voltage value of the terminal in the fuel injection valve after the energization control unit that controls the start and stop of energization of the coil by the power supply unit and the energization control unit stops the energization. The gist is to include a voltage acquisition unit to be acquired and a correction unit that performs correction processing to correct a detection error of the current value detected by the current detection unit based on the voltage value acquired by the voltage acquisition unit. do.

An error may occur between the current value detected by the current detection unit and the actual current value due to the difference in the elements constituting the current detection unit. By the way, when the energization control unit stops energization, a voltage (induced electromotive force) is generated at the terminal of the fuel injection valve by electromagnetic induction based on the change in the magnetic field in the coil of the fuel injection valve. The mode of change of the voltage (induced electromotive force) after the application is stopped is the same if the current flowing through the coil of the fuel injection valve is the same, but is similarly different if the current flowing through the coil is different.

Therefore, the voltage acquisition unit acquires the voltage value at the terminal of the fuel injection valve after the energization is stopped, and the correction unit obtains the detection error of the current value detected by the current detection unit based on the acquired voltage value. It is configured to perform a correction process for correction. As a result, the detection error of the current value can be appropriately corrected.

The figure which shows the schematic structure of the engine control system. The block diagram which shows the structure of an ECU. The figure which shows the structure and the state of a fuel injection valve. A timing chart for explaining the driving operation of the fuel injection valve. The figure which shows the relationship between a drive current and an induced electromotive force. The figure which shows the drive current at the time of calculating a correction value. A flowchart showing a correction value calculation process. A flowchart showing a current value setting process. (A) is a diagram showing a second drive control, and (b) is a diagram showing a first drive control. The flowchart which shows the correction value calculation process of 2nd Embodiment. The flowchart which shows the current value setting process of 2nd Embodiment.

Hereinafter, embodiments will be described. In the following embodiments, parts that are the same or equal to each other are designated by the same reference numerals in the drawings, and the description thereof will be incorporated for the parts having the same reference numerals. In this embodiment, it is embodied as an engine control system that controls a gasoline engine for a vehicle.

(First Embodiment)
The schematic configuration of the engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an in-cylinder injection type multi-cylinder internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided on the downstream side of the air cleaner 13. ing. On the downstream side of the air flow meter 14, a throttle valve 16 whose opening degree is adjusted by a motor 15 and a throttle opening degree sensor 17 for detecting the opening degree (throttle opening degree) of the throttle valve 16 are provided.

A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. An intake manifold 20 for introducing air into each cylinder 21 of the engine 11 is connected to the surge tank 18, and an electromagnetic fuel injection valve 30 for directly injecting fuel into each cylinder 21 of the engine 11 is provided in each cylinder 21 of the engine 11. It is installed. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder 21, and the air-fuel mixture in the cylinder is ignited by the spark discharge of the spark plug 22 of each cylinder 21.

The exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) that detects the air-fuel ratio or rich / lean of the air-fuel mixture based on the exhaust gas, and is downstream of the exhaust gas sensor 24. Is provided with a catalyst 25 such as a three-way catalyst that purifies the exhaust gas.

A cooling water temperature sensor 26 for detecting the cooling water temperature and a knock sensor 27 for detecting knocking are attached to the cylinder block of the engine 11. A crank angle sensor 29 that outputs a pulse signal each time the crank shaft 28 rotates a predetermined crank angle is attached to the outer peripheral side of the crank shaft 28, and the crank angle and engine rotation are based on the crank angle signal of the crank angle sensor 29. The speed is detected.

The outputs of these various sensors are input to the ECU 40. The ECU 40 is an electronic control unit mainly composed of a microcomputer, and performs various controls of the engine 11 by using detection signals of various sensors. The ECU 40 calculates the fuel injection amount according to the engine operating state to control the fuel injection of the fuel injection valve 30, and also controls the ignition timing of the spark plug 22.

Electric power is supplied to the spark plug 22 and the fuel injection valve 30 from the vehicle-mounted battery 51. When the voltage of the battery 51 is low, the alternator 52 connected to the output shaft of the engine 11 is rotated to supply electric power to the battery 51, so that the battery 51 has a predetermined voltage (in the present embodiment). It is charged to 12V).

As shown in FIG. 2, the ECU 40 includes a microcomputer 41 for engine control (a microcomputer for controlling the engine 11), a drive IC 42 for driving an injector (a drive IC for a fuel injection valve 30), and a voltage switching circuit 43a. It includes 43b, current detection circuits 44a, 44b, and the like. The microcomputer 41 corresponds to the "fuel injection control device". The microcomputer 41 calculates the required injection amount according to the engine operating state (for example, engine speed, engine load, etc.), generates a drive pulse from the injection time calculated based on the required injection amount, and outputs the drive pulse to the drive IC 42. do. The drive IC 42 opens and drives the fuel injection valve 30 based on the drive pulse to inject fuel corresponding to the required injection amount.

The voltage switching circuits 43a and 43b are circuits for switching the driving voltage applied to the fuel injection valve 30 of each cylinder 21 between the high voltage V2 and the low voltage V1. Specifically, the voltage switching circuits 43a and 43b supply a drive current to the coil 31 of the fuel injection valve 30 from either the low-voltage power supply unit 45 or the high-voltage power supply unit 46 by turning on / off a switching element (not shown). ..

The low-voltage power supply unit 45 has a low-voltage output circuit that applies the battery voltage (low voltage V1) of the battery 51 to the fuel injection valve 30. The high-voltage power supply unit 46 has a high-voltage output circuit (boost circuit) that applies a high voltage V2 (boost voltage) that boosts the battery voltage to 40V to 70V to the fuel injection valve 30.

When the fuel injection valve 30 is driven to open by the drive pulse, the low voltage V1 and the high voltage V2 are switched and applied to the fuel injection valve 30 in chronological order. In this case, the high voltage V2 is applied at the initial stage of valve opening to ensure the valve opening responsiveness of the fuel injection valve 30, and the low voltage V1 is subsequently applied to ensure the valve opening state of the fuel injection valve 30. Is retained.

The current detection circuits 44a and 44b correspond to the "current detection unit" and detect the current value of the energization current (drive current) when the fuel injection valve 30 is driven to open, and the detection result is transmitted to the drive IC 42. It is output sequentially. The current detection circuits 44a and 44b may have a well-known configuration, and have, for example, a shunt resistor and a comparator.

In the present embodiment, the high-voltage power supply unit 46, the low-voltage power supply unit 45, the fuel injection valve 30 driven by the power supply from each of these power supply units, and the current detection circuits 44a and 44b for detecting the drive current of the fuel injection valve. A system including the above corresponds to a fuel injection system.

Further, in the present embodiment, the engine 11 is a 4-cylinder engine, and fuel injection is performed by outputting injection pulses in the intake stroke and the compression stroke as fuel injection by the fuel injection valve 30 for each cylinder 21. The combustion order of the cylinders 21 of # 1 to # 4 is # 1 → # 2 → # 3 → # 4. In this case, in the two cylinders 21 whose combustion order is continuous in the front-rear direction, there is a concern that the fuel injection periods by the fuel injection valves 30 overlap.

Therefore, in the configuration of FIG. 2, in the engine 11 which is a 4-cylinder engine, two cylinders 21 having a combustion order of every other are grouped into drive groups 1 and 2, and voltage switching is performed for each drive group. Circuits 43a and 43b and current detection circuits 44a and 44b are provided. That is, the voltage switching circuit 43a and the current detection circuit 44a of the drive group 1 are configured to perform voltage switching and current detection for the fuel injection valves 30 of the cylinders 21 of # 1 and # 3. Further, the voltage switching circuit 43b and the current detection circuit 44b of the drive group 2 are configured to perform voltage switching and current detection for the fuel injection valves 30 of the cylinders 21 of # 2 and # 4. As a result, each fuel injection valve 30 is driven by the drive system for each of the drive groups 1 and 2. Then, due to the fact that fuel injection is performed in the intake stroke and the compression stroke in each cylinder 21, even if the fuel injection periods overlap in the two cylinders 21 whose combustion order is continuous in the front-rear direction, each cylinder The fuel injection of 21 is properly carried out.

Here, the fuel injection valve 30 will be described with reference to FIG. The fuel injection valve 30 has a coil 31 that generates an electromagnetic force by energization, a needle 33 (valve body) that is integrally driven with a plunger 32 (movable core) by the electromagnetic force, and a valve closing direction of the plunger 32. It has a spring member 34 that urges in the opposite direction. When the needle 33 moves to the valve opening position against the urging force of the spring member 34, the fuel injection valve 30 is opened and fuel injection is performed. Then, when the energization of the coil 31 is stopped due to the fall of the drive pulse, the plunger 32 and the needle 33 return to the valve closed position, so that the fuel injection valve 30 is closed and the fuel injection is stopped. In the following description, the position where the plunger 32 hits the stopper 35 and further movement in the valve opening direction is restricted is referred to as a “full lift position” of the needle 33.

Next, the driving operation of the fuel injection valve 30 will be described with reference to FIG.

At time ta1, a high voltage V2 whose battery voltage is boosted with the rise of the drive pulse is applied to the fuel injection valve 30. At time ta2, when the current value of the drive current reaches a predetermined peak value Ip, the application of the high voltage V2 is stopped. At this time, the needle lift is started at the timing when the current value of the drive current reaches the peak value Ip or the timing immediately before that, and the fuel injection is started along with the needle lift. Whether or not the current value of the drive current has reached the peak value Ip is determined based on the current value of the drive current detected by the current detection circuits 44a and 44b. That is, in the boosting period (ta1 to ta2), the drive IC 42 determines whether or not the current value of the drive current is equal to or higher than the peak value Ip, and when the current value of the drive current ≥ the peak value Ip, the voltage is switched. The circuits 43a and 43b switch the applied voltage (stop applying V2).

When the drive current falls below a predetermined current threshold value Ih at time ta3, a low voltage V1 which is a battery voltage is applied to the fuel injection valve 30. Whether or not the current value of the drive current is below the current threshold value Ih is determined based on the current value of the drive current detected by the current detection circuits 44a and 44b. That is, in the application stop period (ta2 to ta3), the drive IC 42 determines whether or not the current value of the drive current is equal to or less than the current threshold value Ih, and when the current value of the drive current ≤ the current threshold value Ih, the voltage is applied. The switching circuits 43a and 43b switch the applied voltage (start applying V1).

After that, the low voltage V1 is repeatedly applied and stopped so that a constant current is maintained. For example, when the detected current value is equal to or less than the first target current value Ia1, the low voltage V1 is applied, and the detected current value becomes higher than the first target current value Ia1 by a certain value or more. In that case, the application of the low voltage V1 is stopped. As a result, after the needle 33 reaches the full lift position, the full lift state is maintained and fuel injection is continued. After that, when the drive pulse is turned off at time ta5, the voltage application to the fuel injection valve 30 is stopped, and the drive current becomes zero. Then, the needle lift is terminated when the coil energization of the fuel injection valve 30 is stopped, and the fuel injection is stopped accordingly.

In this way, the fuel injection valve 30 is controlled based on the current value of the drive current, and the current value of the drive current is detected by the current detection circuits 44a and 44b. However, the current detection circuits 44a and 44b have circuit elements such as a shunt resistor, and the actual current value (actual current value) and the detected current value (detection current) are caused by differences in the circuit elements and the like. There may be an error between the value and the value. Therefore, when the fuel injection valve 30 is driven and controlled based on the detected current value, there is a possibility that an error may occur in the timing at which the needle 33 (valve body) is in the valve open state or the valve closed state due to an error from the actual current value. (That is, there may be an error in fuel injection time). That is, there is a possibility that an error may occur in the fuel injection amount.

Therefore, the ECU 40 of the present embodiment is provided with a configuration and processing for appropriately correcting the detection error of the current value. The details will be described below.

First, the principle for grasping the detection error of the current value will be described. It is known that after the energization of the fuel injection valve 30 is stopped (after the voltage application is stopped), the magnetic flux in the coil 31 changes based on the current change, and an induced electromotive force is generated. This induced electromotive force should be the same when the energization is stopped while the drive current of the same actual current value is flowing, if the conditions (position of the needle 33, energization time, etc.) are the same. be. However, when the energization is stopped while the drive currents having different actual current values are flowing, the induced electromotive force is different even if the conditions are the same. This is because the change in magnetic flux after the energization is stopped differs depending on the magnitude of the drive current (actual current value) flowing through the coil 31.

Specifically, as shown in FIG. 5, after the energization of the coil 31 is stopped, the voltage value (induced electromotive force) takes a maximum value Vmax for a certain period of time (time T3 to T4), and then (after time T4). ), Gradually decrease. At that time, the slope at the time of gradual decrease differs depending on the actual current value of the drive current at the time of energization. More specifically, as the actual current value of the drive current when energized is larger (indicated by the solid line), the voltage value gradually decreases as compared with the case where the actual current value is smaller (indicated by the broken line). That is, the smaller the actual current value of the drive current when energized, the sharper the decrease is compared with the case where the actual current value is large. Therefore, in order to correct the detection error between the actual current value and the detected current value, it is sufficient to compare the slopes of the voltage values when the current value is gradually reduced.

That is, when the inclination is gentle compared to the inclination of the reference voltage value, it is judged that the actual current value is larger than the current value corresponding to the reference voltage value, and the detected current value is increased. (Or correction to reduce the indicated current value) may be performed. At that time, it is considered that the gentler the slope of the detected voltage value is, the larger the error is compared with the slope of the reference voltage value, and the correction to make the detected current value larger (correction to make the indicated current value smaller). ) Should be performed. The indicated current value is a current value instructed by the microcomputer 41 to the drive IC 42 when the fuel injection valve 30 is driven and controlled, and serves as a criterion (comparison target) for the detected current value. It is a peak value Ip, a current threshold value Ih, a first target current value Ia1, and the like.

Similarly, when the slope is steep compared to the slope of the reference voltage value, it is judged that the actual current value is smaller than the current value corresponding to the reference voltage value, and the detected current value is set. A correction for reducing the value (or a correction for increasing the indicated current value) may be performed. At that time, the steeper the slope of the detected voltage value as compared with the slope of the reference voltage value, the larger the error, and the correction to make the detected current value smaller (or the indicated current value to be larger). Correction) may be performed.

In this embodiment, the detection error is corrected by correcting the indicated current value. Further, the slope of the voltage value may be grasped by any method. For example, the slope of the voltage value may be specified based on the amount of change in the voltage value in a predetermined time, or the slope of the voltage value may be specified based on the time from the maximum value Vmax to the decrease to the predetermined voltage value. good. Further, the slope of the voltage value at a predetermined voltage value may be calculated by differentiation or the like.

In the present embodiment, the microcomputer 41 gradually decreases from the time T5 when the detected voltage value becomes the initial value Vs smaller than the maximum value Vmax to the time T6 and T7 when the detected voltage value becomes the final value Ve smaller than the initial value. Is obtained, and the slope of the voltage value is specified based on this gradual decrease time. The initial value Vs and the final value Ve are set in advance according to the maximum value Vmax of the dielectric electromotive force (voltage value).

Therefore, in the present embodiment, the detection error of the current value is corrected based on the voltage value (dielectric electromotive force) after the energization is stopped. Therefore, a voltage detection circuit 47 for detecting the voltage value at the terminal (minus terminal in this embodiment) of the fuel injection valve 30 is provided. The voltage value detected by the voltage detection circuit 47 is configured to be input to the microcomputer 41.

Further, in order to detect the voltage value related to the dielectric electromotive force, after stopping the energization of the fuel injection valve 30 between the negative terminal of the fuel injection valve 30 and the high-voltage power supply unit 46, the fuel injection valve 30 An electric path L1 is provided to allow current to flow from the negative terminal. A diode 48 as a reflux mechanism is provided in the electric path L1. The diode 48 is provided so as to allow a current from the negative terminal of the fuel injection valve 30 to the high voltage power supply unit 46. As a result, when dielectric electromotive force is generated, a current flows quickly from the negative terminal of the fuel injection valve 30 to the high-voltage power supply unit 46.

In the present embodiment, electric power (energy) is returned to the high-voltage power supply unit 46, but the connection destination may be arbitrarily changed as long as the voltage value can be detected. For example, it may be connected to the ground via any resistor. Further, although the voltage value of the negative terminal of the fuel injection valve 30 is detected, the voltage value of the positive terminal may be detected.

The microcomputer 41 has a function as an energization control unit 41a that controls energization start and energization stop of the coil 31. Further, the microcomputer 41 functions as a voltage acquisition unit 41b that acquires the voltage value of the negative terminal of the fuel injection valve 30 and the voltage value detected by the voltage detection circuit 47 after stopping the energization of the coil 31. I have. Further, the microcomputer 41 has a function as a correction unit 41c that performs a correction process for correcting a detection error of the current value detected by the current detection circuits 44a and 44b based on the acquired voltage value. More specifically, the microcomputer 41 calculates the correction value based on the comparison between the slope of the acquired voltage value and the slope of the reference voltage value. Then, when the fuel injection valve 30 is driven, the microcomputer 41 corrects the indicated current value (peak value, threshold value, target current value, etc.) by using the correction value. As a result, the detection error of the current value detected by the current detection circuit 44 is appropriately corrected.

By the way, when the needle 33 moves away from the coil 31 after the energization is stopped, it affects the change in the magnetic flux of the coil 31. In other words, it affects the dielectric electromotive force and may cause an error (it may not be possible to calculate an appropriate correction value).

Therefore, when calculating the correction value, the microcomputer 41 non-opens the coil 31 under the condition that the needle 33 remains in the valve closed state, and acquires the voltage value detected in the non-open valve energized state. .. Then, the microcomputer 41 calculates the correction value based on this voltage value.

Further, even if the voltage is applied and stopped so that the current value of the drive current becomes constant, the drive current changes until a predetermined time elapses after the start of energization. If the energization is stopped while the drive current is changing, it may affect the change in the magnetic flux of the coil 31. In other words, it affects the dielectric electromotive force and may cause an error (it may not be possible to calculate an appropriate correction value).

Therefore, when calculating the correction value, the microcomputer 41 controls so that a constant current having a smaller value flows as a drive current as compared with the case where the correction value is not calculated (normal fuel injection control). Specifically, when calculating the correction value, the microcomputer 41 controls so that a constant drive current flows with reference to the second target current value Ia2, which is lower than the first target current value Ia1.

That is, as shown in FIG. 6, the drive IC 42 applies a high voltage V2 with the rise of the drive pulse. Then, when the detected current value becomes the second target current value Ia2 or more, the drive IC 42 stops applying the high voltage V2. After that, when the detected current value becomes the second target current value Ia2 or less, the drive IC 42 applies a low voltage V1 until the drive pulse is turned off, and is equal to or more than a certain value than the second target current value Ia. When the voltage becomes high, the application of the low voltage V1 is stopped. As a result, the change in magnetic flux based on the change in the drive current during energization can be quickly converged, and the correction value can be calculated accurately after the energization is stopped. Therefore, the microcomputer 41 functions as a constant current control unit.

Next, a correction value calculation process for calculating the correction value will be described with reference to FIG. 7. This correction value calculation process is executed by the microcomputer 41 at predetermined intervals, and is repeated until the correction value is calculated (determined). The correction value may be calculated at predetermined time intervals, for example, once a day or once when the ignition switch is turned on.

The correction value calculation process is configured to be executed for each cylinder 21. Further, the correction value calculation process is configured to be executed evenly for each cylinder 21. For example, the correction value calculation process is executed by changing the target cylinder 21 in the order of # 1 → # 2 → # 3 → # 4. In the following description, the target cylinder 21 in the correction value calculation process this time may be simply referred to as the target cylinder 21.

In the correction value calculation process, the microcomputer 41 first determines whether or not fuel injection is required (step S11). That is, as described above, when calculating the correction value, it is necessary to acquire the voltage value detected in the state where the valve is not opened and energized. Therefore, in step S11, the microcomputer 41 determines whether or not fuel injection is required. For example, the microcomputer 41 determines that fuel injection is required when the fuel injection amount calculated based on the engine operating state is not 0, and when the fuel injection amount is 0, the fuel injection is performed. Determine that it is not required.

If the determination result in step S11 is affirmative (when fuel injection is required), the microcomputer 41 ends the correction value calculation process without calculating the correction value. On the other hand, when the determination result in step S11 is negative (when fuel injection is not required), the microcomputer 41 proceeds to step S12 in order to calculate the correction value.

If the determination result in step S11 is negative, the microcomputer 41 performs the current value setting process shown in FIG. 8 (step S12), and proceeds to step S13. In this current value setting process, the second target current value Ia2 is instructed, the correction ratio γ is calculated, and the like. The current value setting process will be described in detail later.

Then, the microcomputer 41 energizes (drives) the fuel injection valve 30 of the target cylinder 21 based on the second target current value Ia2 instructed in the current value setting process (step S13). Specifically, the microcomputer 41 outputs a drive pulse to the drive IC 42 after the second target current value Ia2 is instructed to the drive IC 42.

The drive IC 42 applies a high voltage V2 to the fuel injection valve 30 of the target cylinder 21 as the drive pulse rises. Then, when the detected current values of the current detection circuits 44a and 44b become equal to or higher than the second target current value Ia2, the drive IC 42 stops applying the high voltage V2. After that, when the detected current value becomes the second target current value Ia2 or less until the drive pulse is turned off, the drive IC 42 applies a low voltage V1 to the fuel injection valve 30 of the target cylinder 21. do. Further, when the drive IC 42 becomes higher than the second target current value Ia2 by a certain value or more, the drive IC 42 stops applying the low voltage V1. After the lapse of a predetermined time, the microcomputer 41 stops the output of the drive pulse, stops the energization of the fuel injection valve 30 of the target cylinder 21 (stops the voltage application), and proceeds to step S14. By this step S13, the microcomputer 41 functions as a constant current control unit.

After stopping the energization, the microcomputer 41 acquires the voltage value at the negative terminal of the fuel injection valve 30 of the target cylinder 21 from the voltage detection circuit 47 (step S14). Then, the microcomputer 41 acquires the gradual decrease time as the slope of the voltage value based on the acquired voltage value, and stores it in the storage unit provided in the ECU 40 (step S15). Specifically, the microcomputer 41 acquires the gradual decrease time from the time when the acquired voltage value becomes the initial value Vs to the time when the acquired voltage value becomes the final value Ve, and stores it in the storage unit. At that time, the number of acquisitions of the gradual decrease time (that is, the number of times the dielectric electromotive force is detected) is also stored. That is, 1 is added to the number of acquisitions.

The gradual decrease time and the number of acquisitions are stored separately for each target cylinder 21. That is, when targeting the cylinder 21 of # 1, it is stored in the storage unit that it is the gradual decrease time in the cylinder 21 of # 1 and the number of acquisitions in the cylinder 21 of # 1. The same applies to the other cylinders 21 (# 2 to 4).

After that, the microcomputer 41 determines whether or not the number of acquisitions has reached a predetermined number (for example, 40 times) or more (step S16). In step S16, it is determined whether or not the number of acquisitions in each cylinder 21 has reached a predetermined number or more. This predetermined number of times may be arbitrarily changed, and may be changed to any number of times, for example, 40 to 100 times. If the determination result in step S16 is negative, the correction value calculation process is terminated, and if the determination result in step S16 is affirmative, the process proceeds to step S17.

If the determination result in step S16 is affirmative, the microcomputer 41 reads the gradual decrease time for the number of acquisitions for each cylinder 21 and calculates the average value (average of the gradual decrease time) for each of the drive groups 1 and 2 (step S17). ). Then, the microcomputer 41 compares the average values of the drive groups 1 and 2 and determines whether or not there is a difference in the average values (step S18).

In step S18, the microcomputer 41 determines that there is a difference, for example, when the difference between the average values in the drive groups 1 and 2 is equal to or greater than the threshold value. The threshold value is 0 or a value near 0, and is set in advance. That is, in steps S17 and 18, it is determined whether or not the slopes of the voltage values (induced electromotive forces) in the drive groups 1 and 2 are the same (whether or not there is a difference). In this embodiment, the determination is made based on the difference, but the determination may be made based on the ratio.

If the determination result in step S18 is affirmative (if there is a difference), the correction value calculation process is terminated. On the other hand, when the determination result in step S18 is negative (when there is no difference), the microcomputer 41 determines the calculated correction ratio γ as the correction value (correction coefficient) in the current value setting process and stores it in the storage unit. (Step S19). In the current value setting process, the correction ratio γ is calculated for each cylinder 21 (described later). Therefore, in step S19, the correction ratio γ for each cylinder 21 is determined and stored as a correction value for each cylinder 21. The correction ratio γ is stored for the number of acquisitions. Therefore, the correction ratio γ determined as the correction value in step S19 may be the latest correction ratio γ or the average value of the stored correction ratio γ.

Further, the microcomputer 41 sets the correction completion flag in the storage unit in step S19. Then, the correction value calculation process is completed. When this correction completion flag is set, the correction value calculation process is not executed. The correction completion flag is reset at any time. For example, it may be configured to be reset at the predetermined time described above. As a result, the correction value is calculated (fixed) at predetermined time intervals.

As described above, in the correction value calculation process, when the voltage value varies between the cylinders 21, it is assumed that the appropriate correction ratio γ has not been calculated, and the correction value is repeatedly corrected until the appropriate correction ratio γ is calculated. The calculation process is executed. On the other hand, if there is no variation in the voltage value between the cylinders 21, it is assumed that an appropriate correction ratio γ has been calculated, and the correction ratio γ is determined as the correction value.

Next, the current value setting process in step S12 will be described with reference to FIG.

In the current value setting process, first, the microcomputer 41 determines whether or not the correction value calculation process has already been executed for the target cylinder 21 and the result (previous result) is stored in the storage unit ( Step S21). The previous result is the slope of the voltage value (gradual decrease time) after the second target current value Ia2 instructed when the previous correction value calculation process was executed and the drive control based on the second target current value Ia2. ).

If this determination result is negative, the microcomputer 41 determines a predetermined initial value as the second target current value Ia2 to be instructed this time (step S22). That is, when the second target current value Ia2 is determined for the first time, the initial value is set to the second target current value Ia2. The initial value of the second target current value Ia2 is predetermined and stored in the storage unit.

On the other hand, if the determination result in step S21 is affirmative, the microcomputer 41 determines the second target current value Ia2 to be instructed this time based on the previous result (step S23). In step S23, the microcomputer 41 compares the slope of the voltage value acquired last time with the slope of the voltage value to be used as a reference, corrects the previous second target current value Ia2, and indicates the second target this time. The current value Ia2 is calculated.

That is, as described above, when the microcomputer 41 is gently inclined as compared with the inclination of the reference voltage value, the actual current value in the previous time corresponds to the reference current value (reference voltage value). It can be judged that it is larger than the current value). Therefore, when the microcomputer 41 tilts gently as compared with the slope of the reference voltage value, the second target current value Ia2 instructed this time is made smaller than the second target current value Ia2 in the previous time. Make corrections.

On the other hand, when the current value is steeply inclined, it can be determined that the actual current value in the previous time is smaller than the reference current value. Therefore, when the microcomputer 41 is steeply inclined as compared with the inclination of the reference voltage value, the second target current value Ia2 instructed this time is compared with the second target current value Ia2 in the previous time. Make a correction to make it larger.

The slope of the reference voltage value may be the slope of the voltage value in a predetermined cylinder 21 (for example, the cylinder 21 of # 1), or the slope of the voltage value measured in advance by an experiment (determination). Value). Further, in the present embodiment, the slope of the voltage value is specified by the gradual decrease time. When the slope of the reference voltage value is a predetermined cylinder 21, the detection of the current value detected by the other current detection circuits 44a and 44b is based on any one of the plurality of current detection circuits 44a and 44b. The error will be corrected.

More specifically, in step S23, the second target current value Ia2 specified this time is calculated based on the mathematical formula (1). That is, the constant β and the second target specified last time are obtained by dividing the reference gradual decrease time (slope of the reference voltage value) by the previously acquired gradual decrease time (slope of the voltage value acquired last time). By multiplying the current value Ia2, the second target current value specified this time is calculated. An appropriate value is set for the constant β by an experiment or the like, and the constant β is stored in the storage unit.

Second target current value Ia2 specified this time = (reference diminishing time / diminishing time acquired last time) × constant β × second target current value Ia2 specified last time (1)
As a result, in step S23, the microcomputer 41 instructs the second target this time so that the slope of the reference voltage value and the slope of the acquired voltage value match (at least so that the difference is smaller than the previous time). The current value Ia2 is calculated.

Further, the microcomputer 41 calculates the correction ratio γ by dividing the second target current value Ia2 instructed this time calculated in step S23 by the initial value of the second target current value Ia2 (step S24). The correction ratio γ is calculated for each target cylinder 21. Therefore, the microcomputer 41 stores the calculated correction ratio γ in the storage unit in association with the cylinder 21 which is the target in the correction value calculation process this time.

After that, the microcomputer 41 determines whether or not the number of acquisitions is equal to or greater than a predetermined number (step S25). In step S25, it is determined whether or not the number of acquisitions in the target cylinder 21 is equal to or greater than the predetermined number of acquisitions. The predetermined number of times is the same as the predetermined number of times in step S16. If this determination result is affirmative, the microcomputer 41 resets the gradual decrease time and the number of acquisitions stored in association with the target cylinder 21 (step S26). The gradual decrease time and the number of acquisitions stored in association with all the cylinders 21 may be reset.

If the determination result in step S25 is negative, or after the processes in steps S22 and S26, the microcomputer 41 instructs the drive IC 42 to instruct the drive IC 42 to have the second target current value Ia2 (step S27).

More specifically, when the determination result in step S25 is negative, or after the processing in step S26, the microcomputer 41 instructs the drive IC 42 of the second target current value Ia2 calculated in step S23. Further, after the processing of step S22, the microcomputer 41 instructs the drive IC 42 of the second target current value Ia2 (initial value) determined in step S22. After that, the current value setting process is terminated.

Then, the correction value determined in the correction calculation process is used when driving and controlling the fuel injection valve 30. That is, the microcomputer 41 has an indicated current value (corrected indicated current) calculated by multiplying the indicated current value instructed to the drive IC 42, such as the peak value Ip, the current threshold value Ih, and the first target current value Ia1, by the correction value. Value) is instructed to the drive IC 42. More specifically, the microcomputer 41 corrects the corrected peak value Ip by multiplying the initial value of the peak value Ip, the initial value of the current threshold value Ih, and the initial value of the first target current value Ia1 by the correction values. The later current threshold value Ih and the corrected first target current value Ia1 are calculated. Then, the corrected indicated current value is instructed to the drive IC 42. At that time, the correction value to be multiplied is a correction value corresponding to the cylinder 21 of the fuel injection valve 30 to be driven.

The drive IC 42 performs drive control based on these corrected indicated current values. For example, the drive IC 42 applies a high voltage V2 to the fuel injection valve 30 with the rise of the drive pulse, and when the detected current value reaches the corrected peak value Ip by the current detection circuits 44a and 44b, the high voltage V2 Stop the application. Then, when the detected current value falls below the corrected current threshold value Ih, the drive IC 42 applies the low voltage V1 to the fuel injection valve 30. After that, when the detected current value becomes equal to or less than the corrected first target current value Ia1, the drive IC 42 applies a low voltage V1 and is higher than the corrected first target current value Ia1 by a certain value or more. When this happens, the application of the low voltage V1 is stopped.

The detected current value detected by the current detection circuits 44a and 44b has a detection error with the actual current value, but the indicated current value is corrected based on the correction value so as to cancel it. Therefore, the detection error of the current value detected by the current detection circuits 44a and 44b is appropriately corrected. Further, since the correction value is calculated so that there is no difference between the cylinders 21, variation in each fuel injection valve 30 (cylinder 21) is suppressed by driving control based on the corrected indicated current value.

According to the first embodiment, the following excellent effects can be obtained.

An error may occur between the detected current value detected by the current detection circuits 44a and 44b and the actual current value due to differences in the elements constituting the current detection circuits 44a and 44b. By the way, after the microcomputer 41 stops energization, a voltage (induced electromotive force) is generated at the terminal of the fuel injection valve 30 by electromagnetic induction based on the change in the magnetic field in the coil 31 of the fuel injection valve 30. If the drive current (actual current value) flowing through the coil 31 of the fuel injection valve 30 is the same, the change mode of the voltage (induced electromotive force) after the energization is stopped is the same, while the drive current (actual current value) flowing through the coil 31 is the same. If the current value) is different, it will be different as well.

Therefore, the microcomputer 41 acquires the voltage value at the negative terminal of the fuel injection valve 30 after the energization of the fuel injection valve 30 is stopped, and based on the gradient of the acquired voltage value, the detected current value and the actual current value are used. Changed to perform correction processing to correct the detection error of. Thereby, the detection error of the current value can be suitably corrected.

When the needle 33 opens, the movement of the needle 33 after the energization is stopped affects the change in the magnetic flux in the coil 31, and as a result, the induced electromotive force may be affected. Therefore, the microcomputer 41 calculates a correction value based on the voltage value acquired in the state where the valve is not opened and energized, and corrects the detection error by the correction value. As a result, the detection error can be corrected based on the voltage value acquired without being affected by the behavior of the needle 33, and the error can be further suppressed.

The drive current may not be stable (changed) until a predetermined time elapses after the start of energization, and as a result, it affects the change in the magnetic flux of the coil 31. When the change in magnetic flux is affected, an error may occur in the voltage value acquired under the influence even after the energization is stopped. Therefore, when the correction value calculation process is performed, the microcomputer 41 controls the constant current to a smaller value than when the correction value calculation process is not performed. Specifically, the microcomputer 41 specifies a second target current value Ia2 lower than the first target current value Ia1 when performing energization control of the fuel injection valve 30 when calculating the correction value, and the second target A constant current based on the current value Ia2 was allowed to flow. As a result, the change in the magnetic flux of the coil 31 can be quickly converged, and the accuracy of the correction value can be improved.

The time from the maximum value Vmax of the voltage value to the start of attenuation may differ. This time may vary even if there is no difference in the actual current values. Therefore, the correction value is calculated by comparing the attenuation time starting from the time when the attenuation starts from the maximum value Vmax of the acquired voltage value and the end time when the voltage is attenuated to a predetermined voltage as the slope of the voltage value. bottom. As a result, a more appropriate correction value can be calculated, and the detection error can be suitably suppressed.

The microcomputer 41 compared the reference gradual decrease time (slope of the voltage value) with the acquired gradual decrease time (slope of the voltage value), and calculated the correction ratio γ so that there was no difference. Then, when there was no difference between the cylinders 21, the calculated correction ratio γ was determined as the correction value. By correcting the indicated current value based on this correction value, the detection error can be suppressed. Further, when there is no difference between the cylinders 21, the calculated correction ratio γ is determined as the correction value. Therefore, variation can be suppressed between the cylinders 21.

When correcting the detection error, the indicated current value instructed to the drive IC 42 was corrected. As a result, the amount of processing can be reduced as compared with the case where the detected current value is corrected each time the detected current value is acquired. In addition, the voltage value is repeatedly acquired until the number of acquisitions reaches a predetermined number. Thereby, the detection error can be appropriately suppressed.

The microcomputer 41 corrects (corrects) the previously instructed second target current value Ia2 based on the previous result until the average value of the acquired voltage values disappears between the drive groups 1 and 2, and instructs this time. The determination of the second target current value Ia2 is repeated. Therefore, based on the result of one time, it is possible to perform an appropriate correction as compared with the case where the detection error is corrected.

(Second Embodiment)
The second embodiment is different from the first embodiment in that when the correction value is calculated, the drive control method is different. Hereinafter, the points different from those of the first embodiment will be described in detail.

After the energization of the fuel injection valve 30 is completed, the voltage value detected by the voltage detection circuit 47 may differ (error) due to factors other than the current detection circuits 44a and 44b. For example, there is a possibility that a difference may occur due to a difference in wiring resistance, stray capacitance, or the like in the circuit in the ECU 40, the circuit in the fuel injection valve 30, or the like. Therefore, even if the voltage value acquired in the reference cylinder 21 and the voltage value acquired in the other cylinder 21 are compared, it may be due to an element other than the current detection circuits 44a and 44b, or the current value may be detected. It may not be possible to distinguish whether the difference is due to an error, and it may not be possible to calculate an appropriate correction value.

Therefore, in the second embodiment, the difference in voltage value due to elements other than the current detection circuits 44a and 44b (hereinafter, simply referred to as the first error) and the difference in voltage value due to the current value detection error (hereinafter, hereinafter, simply referred to as the first error). The correction value is calculated based on the second error by distinguishing it from the second error). First, the principle for distinguishing between the first error and the second error will be described.

The voltage value Va in FIG. 9A is a voltage value detected (acquired) after driving the fuel injection valve 30 based on the deviation between the detected current value and the second target current value Ia2 and stopping the energization. Shown. That is, when the microcomputer 41 energizes the fuel injection valve 30 based on the second target current value Ia2 in the same manner as in step S13 of the first embodiment, the voltage value acquired thereafter is shown as the voltage value Va. ing. In FIG. 9, the reference voltage value is shown by a solid line.

The drive control for driving the fuel injection valve 30 based on the deviation between the detected current value and the second target current value Ia2 is referred to as the second drive control. As described above, the slope of the voltage value Va includes the first error and the second error.

On the other hand, the voltage value Vb in FIG. 9B indicates a voltage value detected (acquired) after the fuel injection valve 30 is driven by a short drive pulse of a predetermined voltage and the energization is stopped. More specifically, when the microcomputer 41 outputs a short drive pulse and a high voltage V2 is applied to the fuel injection valve 30 during the output period of the short drive pulse, the voltage value acquired thereafter is the voltage value Vb. It is shown as.

The short drive pulse is shorter than the drive pulse in the second drive control and is set at a fixed time. Further, unlike the second drive control, the high voltage V2 is applied without instructing the indicated current value (second target current value Ia2). The drive control for driving the fuel injection valve 30 by energizing a short pulse of a predetermined voltage is referred to as a first drive control. In the present embodiment, the output time of the short drive pulse is set so that the short drive pulse is output until the current value reaches the peak value Ip.

The slope of the voltage value Vb does not include a second error because the high voltage V2 is applied for a short time without instructing the indicated current value. On the other hand, the slope of the voltage value Vb is affected by factors other than the current detection circuits 44a and 44b, so that the first error is included.

Therefore, the second error can be extracted by comparing the voltage value Va with the voltage value Vb. That is, it is possible to remove the first error from the voltage value Va (at least to reduce the influence). When comparing the voltage values, it is desirable to compare the voltage values acquired under the same conditions except that the drive control method is different. For example, it is desirable to compare the acquired voltage values when the same cylinder 21 is driven by changing the drive control method.

Based on the above, in the second embodiment, the correction value calculation process shown in FIG. 10 is performed. The details will be described below.

The correction value calculation process shown in FIG. 10 is executed by the microcomputer 41 at predetermined intervals as in the first embodiment, and is repeated until the correction value is calculated (determined). The correction value calculation process is configured to be executed for each cylinder 21 as in the first embodiment.

In the correction value calculation process, the microcomputer 41 first determines whether or not fuel injection is required (step S111). If the determination result in step S111 is affirmative (when fuel injection is required), the microcomputer 41 ends the correction value calculation process without calculating the correction value. On the other hand, when the determination result in step S111 is negative (when fuel injection is not required), the microcomputer 41 proceeds to step S112 in order to calculate the correction value.

If the determination result in step S111 is negative, the microcomputer 41 determines whether or not the first acquisition number indicating the number of acquisitions of the voltage value after the first drive control is equal to or greater than the first predetermined number (for example, 40 times). Is determined (step S112).

If the determination result in step S112 is negative, the microcomputer 41 energizes the fuel injection valve 30 of the target cylinder 21 in the first drive control (step S113). Specifically, the microcomputer 41 does not instruct the second target current value Ia2, and outputs a short drive pulse to the drive IC 42. The drive IC 42 applies a high voltage V2 with the rise of the short drive pulse. Then, the drive IC 42 stops applying the high voltage V2 as the short drive pulse rises.

After stopping the energization, the microcomputer 41 acquires the voltage value (first acquired voltage value) at the negative terminal of the fuel injection valve 30 of the target cylinder 21 from the voltage detection circuit 47 (step S114). Then, the microcomputer 41 acquires the first gradual decrease time as the slope of the voltage value after the first drive control based on the acquired voltage value, and stores it in the storage unit (step S115). Specifically, the microcomputer 41 acquires the time from the time when the acquired voltage value becomes the initial value Vs to the time when the acquired voltage value becomes the final value Ve as the first gradual decrease time, and stores it in the storage unit. At that time, the number of first acquisitions is also updated (memorized). That is, 1 is added to the first acquisition number.

The first gradual decrease time and the first acquisition number are stored separately for each target cylinder 21. That is, when the cylinder 21 of # 1 is targeted, the storage unit stores that it is the first gradual decrease time in the cylinder 21 of # 1 and the number of first acquisitions in the cylinder 21 of # 1. The same applies to the other cylinders 21 (# 2 to 4).

After that, the microcomputer 41 determines whether or not the number of first acquisitions is equal to or greater than the first predetermined number of times (for example, 40 times) (step S116). In step S116, it is determined whether or not the number of first acquisitions in each cylinder 21 is equal to or greater than the first predetermined number of times. If the determination result in step S116 is negative, the correction value calculation process is terminated, and if the determination result in step S116 is affirmative, the process proceeds to step S117.

If the determination result in step S116 is affirmative, the microcomputer 41 reads out the first gradual decrease time for each cylinder 21 for the first acquisition number, and for each cylinder 21, the average value of the first gradual decrease time (hereinafter, the first). (Shown as an average value) is calculated (step S117). Then, the microcomputer 41 stores the first average value for each cylinder 21 and ends the correction value calculation process.

On the other hand, if the determination result in step S112 is affirmative, the microcomputer 41 shifts to step S118. That is, when the number of first acquisitions is equal to or greater than the predetermined number of times and the first average value is already stored in step S117, the process proceeds to step S118.

The current value setting process shown in FIG. 11 is performed by the microcomputer 41 (step S118), and the process proceeds to step S119. In this current value setting process, the second target current value Ia2 is instructed, the correction ratio γ is calculated, and the like. The current value setting process will be described in detail later.

Then, the microcomputer 41 energizes the fuel injection valve 30 of the target cylinder 21 by the second drive control (step S119). That is, the microcomputer 41 outputs a drive pulse to the drive IC 42 after the second target current value Ia2 is instructed to the drive IC 42.

The drive IC 42 applies a high voltage V2 to the fuel injection valve 30 of the target cylinder 21 as the drive pulse rises. Then, when the detected current values of the current detection circuits 44a and 44b become equal to or higher than the second target current value Ia2, the drive IC 42 stops applying the high voltage V2. After that, when the detected current value becomes the second target current value Ia2 or less until the drive pulse is turned off, the drive IC 42 applies a low voltage V1 to the fuel injection valve 30 of the target cylinder 21. do. Further, when the drive IC 42 becomes higher than the second target current value Ia2 by a certain value or more, the drive IC 42 stops applying the low voltage V1. As a result, the microcomputer 41 causes the fuel injection valve 30 to pass a constant current based on the second target current value Ia2. After a predetermined time has elapsed from the flow of the constant current, the microcomputer 41 stops the output of the drive pulse, stops the energization of the fuel injection valve 30 (stops the voltage application), and proceeds to step S120.

After stopping the energization, the microcomputer 41 acquires the voltage value (second acquired voltage value) at the negative terminal of the fuel injection valve 30 of the target cylinder 21 from the voltage detection circuit 47 (step S120). Then, the microcomputer 41 acquires the second gradual decrease time as the slope of the voltage after the second drive control based on the acquired voltage value, and stores it in the storage unit (step S121). The method for acquiring the second gradual decrease time is the same as the method for acquiring the first gradual decrease time described above. At that time, the second acquisition number indicating the acquisition number of acquisitions of the second gradual decrease time is also stored. That is, 1 is added to the second acquisition number. In addition, the second gradual decrease time and the second acquisition number are stored separately for each target cylinder 21.

After that, the microcomputer 41 determines whether or not the number of second acquisitions is equal to or greater than the second predetermined number of times (for example, 50 times) (step S122). In step S122, the microcomputer 41 determines whether or not the number of second acquisitions in each cylinder 21 is equal to or greater than the second predetermined number of times. If the determination result in step S122 is negative, the microcomputer 41 ends the correction value calculation process, and if the determination result in step S122 is affirmative, the process proceeds to step S123.

If the determination result in step S122 is affirmative, the microcomputer 41 reads out the second gradual decrease time for the second predetermined number of times for each cylinder 21, and for each cylinder 21, the average value of the second gradual decrease time (hereinafter, the second). (Shown as an average value) is calculated (step S123).

Then, the microcomputer 41 reads out the first average value from the storage unit for each cylinder 21. The microcomputer 41 calculates a difference value which is the average of the time difference based on the second error (time difference based on the current value detection error) by subtracting the first average value read from the second average value for each cylinder 21. (Step S124). In step S124, the difference value in the cylinder 21 of # 1 is calculated by subtracting the first average value in the cylinder 21 of # 1 from the second average value in the cylinder 21 of # 1. The same applies to the other cylinders 21.

Then, the microcomputer 41 calculates the average of the difference values for each of the drive groups 1 and 2 based on the difference value in each cylinder 21, and whether or not there is a difference in the average of the difference values between the drive groups 1 and 2 (difference). Is greater than or equal to the threshold value) (step S125). That is, it is determined whether or not there is a difference in the average of the time differences based on the second error between the drive groups 1 and 2.

If the determination result in step S125 is affirmative (if there is a difference), the correction value calculation process is terminated. On the other hand, when the determination result in step S125 is negative (when there is no difference), the microcomputer 41 determines the calculated correction ratio γ as the correction value (correction coefficient) in the current value setting process and stores it in the storage unit. (Step S126). In the current value setting process, the correction ratio γ is calculated for each cylinder 21. Therefore, in step S126, the correction ratio γ for each cylinder 21 is determined and stored as a correction value for each cylinder 21. The correction ratio γ is stored for the second acquisition number of times. Therefore, the correction ratio γ determined as the correction value in step S126 may be the latest correction ratio γ or the average value of the stored correction ratio γ. Further, the correction completion flag is set in step S126. Then, the correction value calculation process is completed.

Next, the current value setting process in step S118 will be described with reference to FIG.

In the current value setting process, first, the microcomputer 41 determines whether or not the current value setting process has already been executed for the target cylinder 21 and the result (previous result) is stored in the storage unit ( Step S131). The previous result is the second target current value Ia2 instructed when step S119 of the previous correction value calculation process is executed, and the voltage value after the second drive control is performed based on the second target current value Ia2. It is the slope of (second gradual decrease time). If this determination result is negative, the microcomputer 41 determines a predetermined initial value as the second target current value Ia2 (step S132).

On the other hand, when the determination result in step S131 is affirmative, the microcomputer 41 determines the second target current value Ia2 to be instructed this time based on the previous result and the first average value (step S133). In step S133, the microcomputer 41 compares the slope of the voltage value acquired after the previous second drive control with the first average value (the slope of the voltage value acquired after the first drive control) to obtain a second error. The time difference based on (the time difference based on the detection error of the current value) is extracted. Then, based on the comparison between the time difference based on the second error and the reference value, the previous second target current value Ia2 is corrected to calculate the second target current value Ia2 instructed this time.

Specifically, the microcomputer 41 subtracts the first average value (the average of the first gradual decrease time) from the second gradual decrease time acquired last time, and extracts the time difference based on the second error. The value obtained by subtracting the first average value from the second gradual decrease time acquired last time may include a time difference due to a difference in drive control as well as a time difference based on the second error. Then, the value is simply shown as a time difference based on the second error.

Then, the microcomputer 41 compares the time difference based on the second error with the reference value, corrects the previous second target current value Ia2, and calculates the current second target current value Ia2. The reference value is a value obtained by subtracting the first average value in the cylinder 21 from the second diminishing time in the predetermined cylinder 21 (for example, the cylinder 21 of # 1). The reference value may be a value measured in advance by an experiment and may be a value (determination value) stored in the storage unit.

Then, when the time difference based on the second error is larger than the reference value, the microcomputer 41 makes the second target current value Ia2 instructed this time smaller than the second target current value Ia2 in the previous time. Make corrections. On the other hand, when the time difference based on the second error is smaller than the second reference value, the microcomputer 41 compares the second target current value Ia2 instructed this time with the second target current value Ia2 in the previous time. Make a correction to make it larger. That is, the second target current value Ia2 to be instructed this time is determined so that the time difference based on the second error matches the reference value.

More specifically, in step S133, the second target current value Ia2 specified this time is calculated based on the mathematical formula (2). That is, the second target current value specified this time is specified by multiplying the value (ratio) calculated by dividing the reference value by the time difference based on the second error by the constant α and the second target current value Ia2 specified last time. Is calculated. An appropriate value is set for the constant α by an experiment or the like, and the constant α is stored in the storage unit.

Second target current value Ia2 specified this time = (reference value / time difference based on second error) x constant α x second target current value Ia2 ... (2) specified last time
As a result, in step S133, the microcomputer 41 calculates the second target current value Ia2 instructed this time so that the reference value and the time difference based on the second error match (at least so that the difference is smaller than the previous time). ..

Further, the microcomputer 41 calculates the correction ratio γ by dividing the second target current value Ia2 instructed this time calculated in step S133 by the initial value of the second target current value Ia2 (step S134). The correction ratio γ is calculated for each target cylinder 21. Therefore, the microcomputer 41 stores the calculated correction ratio γ in the storage unit in association with the cylinder 21 which is the target in the correction value calculation process this time.

After that, the microcomputer 41 determines whether or not the first acquisition number is equal to or more than the first predetermined number and the second acquisition number is equal to or greater than the second predetermined number (step S135). In this step S135, the determination is made based on the number of first acquisitions and the number of second incomes of the target cylinder 21. If this determination result is affirmative, the microcomputer 41 resets the gradual decrease time and the number of acquisitions of the target cylinder 21 (step S136). In step S136, all the gradual decrease times (first gradual decrease time, second gradual decrease time) and acquisition times (first acquisition number, second acquisition number) stored in association with the target cylinder 21 are reset. do. The gradual decrease time and the number of acquisitions in all the cylinders 21 may be reset.

If the determination result in step S135 is negative, or after the processing in steps S132 and S136, the microcomputer 41 instructs the drive IC 42 to instruct the drive IC 42 to have the second target current value Ia2 (step S137).

More specifically, when the determination result in step S135 is negative, or after the processing in step S136, the microcomputer 41 instructs the drive IC 42 of the second target current value Ia2 calculated in step S133. Further, after the process of step S132, the microcomputer 41 instructs the drive IC 42 of the second target current value Ia2 determined in step S132. After that, the current value setting process is terminated.

The correction value determined in this way is used when driving and controlling the fuel injection valve 30, as in the first embodiment. Therefore, the detection error of the current value detected by the current detection circuits 44a and 44b is appropriately corrected. Further, since the correction value is calculated so that there is no difference between the cylinders 21, the variation for each fuel injection valve 30 can be suppressed by performing the drive control based on the corrected indicated current value.

According to the second embodiment, the following excellent effects can be obtained.

An error may occur in the voltage value detected by the voltage detection circuit 47 due to factors other than the current detection circuits 44a and 44b, for example, resistance and stray capacitance in the circuits in the ECU 40 and the fuel injection valve 30.

Therefore, it was decided to compare the second gradual decrease time and the first gradual decrease time, extract the time difference based on the second error, and calculate the correction value based on the time difference based on the second error. The second gradual decrease time includes a time difference based on the second error (time difference based on the detection error of the current value) and a time difference based on the first error (time difference based on the circuit factor) in an overlapping manner. On the other hand, the first gradual decrease time does not include the time difference based on the second error, but the time difference based on the first error is included in the same manner as the second gradual decrease time. Therefore, the time difference based on the second error can be extracted by comparing the second gradual decrease time and the first gradual decrease time. Therefore, by performing the correction process using the extracted time difference based on the second error, the influence of the time difference based on the first error can be suppressed and the correction can be appropriately performed.

(Other embodiments)
The present invention is not limited to the above embodiment, and may be implemented as follows, for example. In the following, the parts that are the same or equal to each other in each embodiment are designated by the same reference numerals, and the description thereof will be incorporated for the parts having the same reference numerals.

In the above embodiment, if the drive current in a predetermined range corresponding to the second target current value Ia2 flows through the fuel injection valve 30, the voltage application method may be changed to any method. For example, when a low voltage V1 is applied, duty control may be performed so that on / off is periodically repeated. Further, the low voltage V1 may be continuously applied. Further, a high voltage V2 may be applied instead of the low voltage V1.

In the above embodiment, the correction process is performed based on the voltage value acquired when the fuel injection valve 30 is not open and energized, but the voltage value acquired when the fuel injection valve 30 is open and energized. The correction process may be performed based on the above.

In the above embodiment, the second target current value Ia2 is set to be smaller than the first target current value Ia1, but it may be set to a larger value.
In the above embodiment, the number of cylinders 21 may be arbitrarily changed.
In the above embodiment, the number and type of indicated current values may be arbitrarily changed.

In the above embodiment, the current detection circuits 44a and 44b may be provided for each cylinder 21. Further, a plurality of high voltage power supply units 46 may be provided. For example, a high-voltage power supply unit 46 may be provided for each of the drive groups 1 and 2. In this case, it is desirable to provide a reflux mechanism (diode 48) for each of the drive groups 1 and 2.

In step S18 of the first embodiment, it is determined whether or not there is a difference in the average values of the drive groups 1 and 2, but it may be determined whether or not there is a difference in the average values of the cylinders 21. .. Similarly, in step S125 of the second embodiment, it may be determined whether or not there is a difference in the average of the difference values in each cylinder 21.

In step S18 of the first embodiment, it is determined whether or not there is a difference between the average values of the drive groups 1 and 2, but the average values of the drive groups 1 and 2 are different from the predetermined reference values. It may be determined whether or not there is. That is, it may be determined whether or not the average value of the drive groups 1 and 2 matches or substantially matches the reference value. The reference value may be a gradual decrease time in any of the cylinders 21, or a value set by an experiment and stored in the storage unit.

In step S125 of the second embodiment, it was determined whether or not there was a difference in the difference values (average) of the drive groups 1 and 2, but the difference values (average) of the drive groups 1 and 2 were predetermined respectively. It may be determined whether or not there is a difference from the reference value. That is, it may be determined whether or not the difference value (average) of the drive groups 1 and 2 matches or substantially matches the reference value. The reference value may be a time difference based on the second error in any of the cylinders 21, or a value set by an experiment and stored in the storage unit.

In the first embodiment, the voltage value was acquired a plurality of times before the correction value was determined, but the correction value may be determined based on the voltage value once. In this case, the process of step S15 of the first embodiment may be omitted. Similarly, in the second embodiment, the voltage values are acquired a plurality of times with different drive controls until the correction value is determined, but each may be obtained once. In this case, the processing of steps S116 and S122 of the second embodiment may be omitted.

In step S18 of the first embodiment, it is determined whether or not there is a difference in the average value of the gradual decrease time, but it may be determined whether or not there is a difference in the slope (gradual decrease time) of the latest voltage value. .. Similarly, in step S125 of the second embodiment, it is determined whether or not there is a difference in the average of the time difference (difference value) based on the second error, but it is determined whether or not there is a difference in the latest difference value. You may.

In step S23 of the first embodiment, the method of calculating the second target current value Ia2 instructed this time is not limited to the mathematical formula (1), and may be any method. For example, the second target current value Ia2 specified this time may be calculated based on the mathematical formula (3). That is, it was obtained by multiplying the value obtained by subtracting the previously acquired gradual decrease time (slope of the previously acquired voltage value) from the reference gradual decrease time (slope of the reference voltage value) by multiplying it by the constant B. The second target current value Ia2 specified this time may be calculated by further multiplying the value obtained by adding 1 to the value by the second target current value Ia2 specified last time. An appropriate value is set for the constant B by an experiment or the like, and the constant B is stored in the storage unit.
Second target current value Ia2 specified this time = ((reference diminishing time-previously acquired diminishing time) x constant B + 1) x second target current value Ia2 ... (3)

In step S133 of the second embodiment, the method of calculating the second target current value Ia2 instructed this time is not limited to the mathematical formula (2), and may be any method. For example, the second target current value Ia2 specified this time may be calculated based on the mathematical formula (4). That is, the second target current value Ia2 previously instructed for the value obtained by multiplying the value obtained by subtracting the time difference based on the second error from the reference value by the constant A and adding 1 to the value obtained by the multiplication is further added. The second target current value specified this time may be calculated by multiplying. An appropriate value is set for the constant A by an experiment or the like, and the constant A is stored in the storage unit.
Second target current value Ia2 specified this time = ((reference value-time difference based on second error) x constant A + 1) x second target current value Ia2 ... (4) specified last time

Further, the second target current value Ia2 specified this time may be calculated based on the mathematical formulas (5) to (7). An appropriate value is set for the constant C by an experiment or the like, and the constant C is stored in the storage unit. Further, the reference 1st gradual decrease time and 2nd gradual decrease time may be the 1st gradual decrease time and the 2nd gradual decrease time in the predetermined cylinder 21, or the 1st gradual decrease time and the 2nd gradual decrease time appropriate by experiments or the like. You may set the time and memorize it.

Reference 1st gradual decrease time-Last acquired 1st gradual decrease time = Detected value D ... (5)
Reference 2nd gradual decrease time-Last acquired 2nd gradual decrease time = Detected value E ... (6)
Second target current value Ia2 specified this time = ((detection value E-detection value D) x constant C + 1) x second target current value Ia2 ... (7) specified last time

In the above embodiment, the output time of the short drive pulse is set so that the short drive pulse is output until the current value reaches the peak value Ip, but the output time is not limited to this and may be arbitrarily changed. .. For example, the output time of the short drive pulse may be set so that the short drive pulse is output after the current value reaches the peak value Ip and before the start of application of the low voltage V1.

30 ... Fuel injection valve, 31 ... Coil, 33 ... Needle, 41 ... Microcomputer, 41a ... Energization control unit, 41b ... Voltage acquisition unit, 41c ... Correction unit, 44a ... Current detection circuit, 44b ... Current detection circuit, 45 ... Low voltage Power supply unit, 46 ... High voltage power supply unit.

Claims (6)

A fuel injection valve (30) having a coil (31) that is energized based on a voltage applied from the power supply units (45, 46) and a valve body (33) that is opened and closed in response to the energization of the coil, and the power supply unit. A fuel injection control device (41) applied to a fuel injection system, comprising a current detection unit (44a, 44b) for detecting a current value when a voltage is applied from the fuel injection system.
An energization control unit (41a) that controls the start and stop of energization of the coil by the power supply unit, and
A voltage acquisition unit (41b) that acquires a voltage value of a terminal in the fuel injection valve after the energization control unit stops energization.
A correction unit (41c) that performs correction processing for correcting a detection error of the current value detected by the current detection unit based on the voltage value acquired by the voltage acquisition unit is provided .
The drive control of the fuel injection valve is based on the first drive control for driving the fuel injection valve by energizing a short pulse of a predetermined voltage, and the deviation between the current value detected by the current detection unit and the predetermined target current value. It is possible to carry out the second drive control for driving the fuel injection valve.
The correction unit has acquired the first acquired voltage value acquired by the voltage acquisition unit when the first drive control is executed and the voltage acquisition unit when the second drive control is executed. A fuel injection control device that performs the correction process based on the difference from the second acquired voltage value. The energization control unit non-opens the energization of the coil under the condition that the valve body remains closed.
The fuel injection control device according to claim 1, wherein the correction unit performs the correction process based on a voltage value acquired in a state where the valve is not opened and energized. A fuel injection control device that maintains a valve open state by passing a predetermined constant current through the coil after the fuel injection valve is opened.
The correction process includes a correction value calculation process for calculating a correction value for correcting the detection error of the current value.
The fuel injection control according to claim 1 or 2, wherein when the correction value calculation process is performed, a constant current control unit for controlling the constant current to a smaller value is provided as compared with the case where the correction value calculation process is not performed. Device. The correction unit compares the attenuation time starting from the time when the energization control unit stops the energization and then starting the attenuation from the maximum value of the acquired voltage value, and ending at the time when the voltage is attenuated to a predetermined voltage. The fuel injection control device according to any one of claims 1 to 3 , wherein a correction value is calculated and the detection error of the current value is corrected based on the correction value. The fuel injection system is provided with a plurality of the fuel injection valves.
The correction unit of claims 1 to 4 performs correction processing for correcting a detection error of the current value based on a voltage value acquired after energizing any one of the plurality of fuel injection valves. The fuel injection control device according to any one of the above. The correction unit according to any one of claims 1 to 4 , wherein the correction unit performs correction processing for correcting the detection error of the current value based on the comparison between the determination value stored in advance and the acquired voltage value. Fuel injection control device.

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